Refactor account preferences model

By breaking the account preferences into their own object we can
offer a settings screen that does only one RPC to change any of
the settings, updating them all en-mass on the server side.  It
makes it easier to add new settings to the code, because we will
only need to modify the database and the model, and not the RPC
interfaces or their service implementations.

Signed-off-by: Shawn O. Pearce <sop@google.com>
12 files changed